Field of the Invention
The present invention relates to an inverter control device and inverter control method, and in particular, relates to an inverter control device that controls a multiple of inverters configured to use the same positive and negative direct current voltage bus lines connected to a power supply and driving a corresponding multiple of motors, and to an inverter control method.
Description of the Related Art
For example, efficiency when driving a motor is extremely important in an application such as a hybrid automobile or electric automobile. Therefore, two-phase modulation is often used as a method of improving efficiency when driving a motor using pulse width modulation (PWM). Two-phase modulation is such that switching of a predetermined one phase of three phases is stopped, because of which switching loss occurring in a switching element can be reduced. Meanwhile, however, two-phase modulation is such that current pulse is large because there are few switchings, because of which there is a problem in that ripple of direct current bus line voltage increases.
This problem is particularly noticeable when a multiple of motors are driven using the same positive and negative direct current voltage bus lines, and increasing the size of a smoothing capacitor is unavoidable, which leads to an increase in cost.
To date, as a control method whereby direct current voltage is smoothed, a method whereby inverter outflow current pulses are displaced, or a method whereby inverter outflow current pulses are neutralized, when driving a multiple of motors using PWM by appropriately displacing phases of carrier waves with respect to the multiple of motors in accordance with motor drive states has been proposed, as disclosed in, for example, Patent Document 1.    Patent Document 1: JP-A-2002-51566
However, the heretofore described control method is such that a separate carrier wave is used for each motor, because of which there is a problem in that an operation load increases. Also, the heretofore described means that does not use two-phase modulation is such that switching loss cannot be reduced, and there is a problem in that an increase in efficiency cannot be expected.